The present invention relates generally to containment booms and, more particularly, to containment booms which are adapted for use in connection with sites of underwater activity which can produce sound or shock waves.
Underwater explosives as well as construction and demolition work, in general, produce sound or shock waves that travel in all directions from the site of activity at a rate of approximately four times the speed it would travel in air. Water is also non-compressible, whereas air is compressible. Thus, water more effectively transmits the energy of the sound or shock wave to the surrounding environments. As a result, underwater explosions or construction or demolition work quite often lead to severe injury or death of large numbers of marine life as a result of the crushing effect the sound or shock waves have on internal air cavities of the marine life. Generally speaking, regulatory agencies require some means for minimizing the impact of underwater detonations.
One approach which has been utilized previously involves the provision of an air curtain, which is simply the result of releasing compressed air below the water surface such that the rising air bubbles form a semi-continuous perimeter about the site of work. The presence of the air bubbles about the perimeter have the effect of dispersing the sound or shock waves produced by the worksite, thereby absorbing the intensity of the sound or shock wave and allowing the transmission of, hopefully, only non-lethal sound or shock waves whose intensity is greatly dissipated as compared to the initial sound or shock waves emanating from the site of work. One problem with this approach is that the air curtain is often dispersed by tidal currents, thereby decreasing its efficacy. Depending on how great the air curtain becomes dispersed, it may have little or no effect.
Therefore, it would be desirable to provide a containment boom which overcomes this deficiency in the art.
A first aspect of the present invention relates to a method of attenuating underwater transmission of sound or shock waves which includes: surrounding a site of underwater activity with a boom system including (i) a support system, (ii) a curtain including a sheet of flexible material which allows water to flow therethrough, the curtain being suspended from the support system such that the curtain extends substantially the entire water column to define a perimeter enclosure, and (iii) a gas injection system including a plurality of outlets which surround the site of underwater activity, the plurality of outlets being positioned between the site of underwater activity and the curtain; and injecting gas into the water through the plurality of outlets to form a gas curtain during performance of an underwater activity capable of generating sound or shock waves, whereby the curtain minimizes dissipation of the gas curtain to improve the efficacy of sound or shock wave attenuation as compared to a gas curtain in the absence of the curtain.
A second aspect of the present invention relates to a method of attenuating underwater transmission of sound or shock waves which includes: surrounding a site of underwater activity with a boom system including (i) a support system, (ii) a curtain including a sheet of flexible material which allows water to flow therethrough, the curtain being suspended from the support system such that an upper end thereof is positioned above the water level and a lower end thereof positioned above the floor of the body of water, (iii) a skirt including a sleeve formed of a material which resists folding and a ballast positioned within the sleeve, the skirt being connected to the lower end of the curtain or to the support system, wherein the curtain and the skirt together extend substantially the entire water column, with the ballast-weighted skirt resting against the floor of the body of water, thereby defining a perimeter, and (iv) a gas injection system including a plurality of outlets which surround the site of underwater activity, the plurality of outlets being positioned between the site of underwater activity and the perimeter; and injecting gas into the water through the plurality of outlets to form a gas curtain during performance of an underwater activity capable of generating sound or shock waves, whereby the curtain minimizes dissipation of the gas curtain to improve the efficacy of sound or shock wave attenuation as compared to a gas curtain in the absence of the curtain and skirt.
A third aspect of the present invention relates to a boom system which includes: a support system; a curtain including a sheet of flexible material which allows water to flow therethrough, the curtain being suspended from the support system such that, upon introduction into a body of water, an upper end thereof is positioned above the water level and a lower end thereof is positioned above the floor of the body of water; and a skirt including a sleeve formed of a deformable material which resists folding and a ballast positioned within the sleeve, the skirt being connected to the lower end of the curtain or to the support system, wherein upon introduction into a body of water the curtain and the skirt together extend substantially the entire water column, with the ballast-weighted skirt resting against the floor of the body of water.